Circuit breaker



May 4 1943- H. D. DORFMAN ETAL 2,318,298

CIRCUIT BREAKER Filed June 24, 1941 2 Sheets-Sheet 1 May 4, 1943` H. D.DORFMAN ETAL. 2,318,298

CIRCUIT BREAKER Filed June 24, 1941 2 Sheets-Sheet 2 ventV vibration. orchatter Patented Mey 4, 1943 Freese Awestnignense meen-le a l'a.,signers to Oom-- pany, East Pittsburgh Pa., a mondano Pennsylvaniaapplication June lr4, 1941, semi No. 399,456 v lzclaims.

invention relates te circuit breakers, and more particularly to circuitbreakers of the type which are manually operable to open or to close Oneobject of the invention is to provide a cir-- cuit breaker havingimproved means to cause .quick opening and closing of the contacts.

Another object of the invention is to provide a circuit breaker havingimproved means for causing the contacts to open a greater distancewithout increasing the size oi the operating mechanism.

Another object of the invention is to provide a circuit breaker withimproved means to preof the contacts when they'are opened or closed.'

Another object of the invention is to provide a circuit breaker withimproved means i'or applying contact pressure to the contacts when saidcontacts are closed:

Another object of the invention is the provision of a circuit breakerhaving improved circuit opening and closing characteristics, and whichis simple in construction and inexpensive to manuiacture.

Another object of the invention is to provide 'a circuit breaker havinga contact a'rm pivoted on af movable switch member and a toggle for.

operating the contact arm to cause a greater separation of the contactsthan ir the contacts w'eremounted in the usual way on the switch member.

Another object of the invention is to provide a circuit breaker withmeans for increasing the contact pressure as the contacts start to open.

Another object of the invention is to provide a circuit breaker withnovel vmeans whereby the pressure applied t the contacts increases asthe contacts wear.

A further object of the invention' is to provide a circuit breaker withimproved means to cause the contacts to open and close with a wiping'vtion, together with additional objects and ad-v vantages thereof, willbe bestunderstood from the following detailed description of several em-.bodiments thereof when read in conjunction with the accompanyingdrawings, in which:

Figure iis a iront elevational view o! a three- 55 (ci. zoo-'61) polecircuit breaker embOdyina the principal ele*- ments of the invention.The .cover has been partly broken away to more clearly show some of theparts of the breaker. Fig. 2 is a vertical sectional view of the circuitbreaker taken substantially on line lI-IIfoi.' Fig. 1 and looking in thedirection of the arrows, the breaker. being shown in closed circuitposition,

Fig. 3 is a vertical sectional view of the circuit breaker similar toPig. 2, but showing the breaker in its tripped open position, Y l Pig. 4is an enlarged detail view of a modi ilcation of the movable contactarm, said arm being shown in closed contact position by the full linesand in its iully open position by the dot and dash lines. Referring toF185.. 1 and 2 of the drawings. the circuit breaker includes a base Ilof molded insulating material on which the several elements o! thebreaker mechanism are mounted. A cover I2 also of molded insulatingmaterial is remov` ably secured to the base and cooperates therewith toform an enclosing housing for the parts oi thel circuit breaker.A Y 25'The circuit breaker is oi the multi-pole type, each pole comprising apair oi' terminals I I and il, one mounted at each end of the base, astak tionary contact Il, an arc extinguisher Il and a movable 'contact2|.l A .common operating mechanism indicated generally at 22 is providedcontacts 2|, and a three pole trip device. serves to effect automaticopening of the three movable contacts 2l in response to predeterminedoverload conditions in the circuit through any pole of the breaker. Eachof the movable contacts 2| is mounted on a contact arm 2l pivotallylsupported intermediate its ends on a pivot pin 20 in the free endsoi* apair of switch arms 21. The arms 21 aremounted on a rectangular tie bar2l of insulating material and are joined by a rectangularsleeve Ilsurrounding the tie bar and secured thereto so that all of the arms 21move as-a unit. A flexible shunt conductor Il connects the-contact arm2l with an angular terminal 32 secured by a screw I3 to one end ot aconductor 35. The other end of the conductor I5 is connected by anexible shunt conductor I1 to a point' near the iree end of s bimetalelement Il, said bimetal element being rigidly secured on the inner endof a conductor Il. The terminal I5 is securedto the outer end or theconductor 4I. Each o! the stationary contacts l1 is mounted on the innerend for simultaneously actuating the three movable' I of a conductor 43having its outer end connected to a corresponding terminal I3.

The electrical circuit for each of the poles is essentially the same andextends from the terminal I3 through the conductor 43, stationarycontact I1, the movable contact 2|, the contact arm 25, the exible shuntconductor 39, the terminal 32, the conductor 35, the flexible shuntconductor 31, the bimetal element 39 and the conductor 4 I to theterminal I 5.

In order to prevent ilashovers between the poles of the breaker,barriers 42 (Figs. 1 and 2) are molded integral with the base II andextend the length of the breaker. When the cover I2 is in place,barriers 45 (Fig. 2) molded integral with said cover are in alignmentwith the barriers 42 and form separate compartments for the poles. Thetie bar 29 is provided with annular projections 49 which t withinrecesses 50 in the barriers 42 to close the openings in the barriersthrough which the tie bar extends.

The operating mechanism for the breaker indicated generally at 22 (Fig.2) is supported on a frame comprising a pair ofirame members 44 insertedin slots in the barriers 42 and suitably secured to the center part ofthe base I I. The operating mechanism includes a forked operating lever41, toggle links 49 and 5|,- a pair of overcenter springs 53 and a.releasable cradle 55 controlled by the trip device 23. The springs 53mounted on the outer end of operating lever 41.v

A manual operating handle 63 integral with the shield 59 projectsthrough the opening 6I to permit manual operation of the breakermechanism.

The toggle links 49 and 5I are pivotally connected by a knee pin 65. Thelink I is pivotally connected by a pivot pin 6T to the arms 21 whichcarry the contact arm for: the center pole and the link 49 is bifurcatedat its outer end and pivotally engages a pin 89 on. the cradle 55 beingvretained in engagementl therewith by the overcenter springs 53 tensionedbetween the knee pin 55 and the outer:` portion. of the operating lever41. The overcenter movementv of the toggle A 49--5I is limited by Stud5E. on the link' 5| just below the knee pin 55 striking a projecin'onz'`on the cradle 55. This projection 58 also acts to positively start thetoggle iny a directiony to cause collapse thereofv when the breaker istripped automatically` in response to an, overload as will be describedlater.`

The arms 2T which pivotally carry the contact arms 25 for all threepoles'r are mounted on the insulating tie bar 29 so thatl the contactsfor all poles are operated simultaneously, and yet: each pole isinsulated from the other poles- An axially disposed metal shaftv 1Iextends through the tie` bar 29 and rotatably supports the tie bar inbracketsv 13 suitably' secured tn thebase II of the breaker.

' overcenter springs Vll are associated with the contact arms 25. These;springs surround contact arm. operating members 19 and are compressedbetween angular brackets ll secured to the pivoted ends of the switcharms 21' and shoulders 83 on the members 19. The springs 11 The cradle55 is f hold the ends of the members 19 in engagement with recesses 85in the inner ends of the contact arms 25. The brackets 8| serve tosupport and guide the members 19, the members 19 extending throughenlarged guide openings in the brackets 8|. Each contactarm 25 and itscooperating toggle member 19 forms a snap action toggle which, in theclosed circuit position, is overcenter in adirection which permits thespring 11 to apply pressure to the contacts.

As previously stated, the trip device 23 includes a bimetal 39 connectedin series in the circuit for each pole of the breaker. The trip devicealso includes a trip bar 81 of molded insulating material pivotallysupported in bearings in the side walls of the breaker base.

Each pole of the breaker is provided with a latch lever 93 pivotallysupported on a U-shaped frame 95 by a pivot pin 91, the frame 95 beingmounted on the base ll. A spring |05 compressed between a bar |91,supported between the legs of the frame, and the latch lever 93, biasessaid lever in a clockwise direction. Clockwise rotation of the latchlever'- 93 is normally prevented by engagement of its latch end with alatch |09* on the free end of the bimetal 39.

A latch member III secured to projections ||3 molded integral with thetrip bar 81 normally engages the latch end of. the cradle 55 and therebyrestrains the cradle 55 in its operative position.

When any one of the bimetal elements 39 is heated a predetermined.amount in response to an overload current, it exes in a direction tounlatch its corresponding lever 93 whereupon the spring |05 rocks thelever 93 in a clockwise direction. During this movement the end of thelever l93 strikes a projection II5 on the trip bar and rocks said tripbar counterclockwise causing the latch member to release the cradle 55.This permits the overcenter.`r springs 53 to actuate the operatingmechanism. and open the contacts as will be more fully described later.

'The trip device is also operated magnetically to instantaneously tripthe breaker on the occurrence of a heavy overload. for instance, 1000%or more of rated 4current or on short circuits in. the circuit of anyone ofthe poles.

.For this purpose each pole of the breaker is provided with anelectromagnety indicated generally at 86 and which includes a U-shapedstationary core I1 through which extends the conductor 35, the conductorbeing suitably insulated from the magnet corev II1. The electromagnetis` also provided with a hinged armature |23 havinga projecting arm I 24which is adapted to engage a projection |4| on the. trip bar 81 and rocksaid bar and the latch member III counterclockwise to trip the breakerwhen the electromagnet` is energized by heavy overload or short circuitcurrent flowing through the conductor 35. 'I'he armature |23 is biased`to unattracted position by a spring |35.

A leaf spring |43 (Fig. 2) disposed in a recess in one of the barriers42 is tensioned against a flat surface of the trip bar 81 to bias thetrip bar to neutral position andk to prevent accidental tripping of thebreaker due to jars or shocks.

The circuit breaker mechanismV is shown in Fig. 2 in the closed circuitposition. When the tripy bar 91 is-rocked in4 unlatching direction inresponse to an overload. current in the circuit of any one of thepoles., the latch III disentritgesv the cradle 55 and permits thesprings 52 to rotate the cradle ina clockwise direction about its pivot55. At the start of this rotation of the cradle 55, the projection 55engages the stud 55 on the toggle link and starts the toggle 49-5lin-the direction to cause it to collapse. .Continued movement of thecradle 55 carries the center line of the toggle'link 45 to the rightofthe line o f action of the springs 53 which then act to complete thecollapse of the toggle. This -rocks the arms 21 and the tie bar 25counterclockwise carrying the contact arms 25 therewithv to open circuitposition.

In the clod circuit position (Fig. 2) the line of action of the spring11 is above the pivot 25 of the contact Yarm 25 and biases the contactarm 25 in a clockwise direction about its pivot 25 to provide contactpressure. When the arms 21 are rocked counterclockwise, as abovedescribed, a tail |45 on the member 15 strikes a projection |41 moldedintegral with the base causing the member 19 to rock clockwise pivotingat its point of contact with the bracket 5| and rocking the contact arm25 counterclockwise about its pivot 25 on the arms 21. 'Ihis movement ofthe contact arm 25 is limited by a projection on said arm striking a pin|49 in the arms 21. The breaker is shown in its tripped open position inFig. 3.

The result of the pivoted contact arm construcvtion and'of the action ofthe overcenter spring 11 is to eilect a greater contact separation whenthe breaker is opened, and also a higher speed of operation of 'thecontacts in both opening and` closing. decreases the possibility ofrestriking of the arc, and also eliminates re-arcing due to vibration ofthe contact arm since the action -oi the contact toggle opposes reboundof the moving contact.

It-may be stated here that the greater separation of the contactsresulting from the action of the toggle 15-25 makes possible the use of`circuit breakers of the type disclosed in circuits carryingsubstantially higher value currents than l has heretofore been possiblewith the required degree of safety. This-resultsl in considerableVeconomy of manufacture, since the same base and operating mechanism maybe utilized for breakers having low capacity rating and high capacityrating by substituting the contact arm of the invention for the priorart contact arm where the movable contact is mounted directly on theswitch arm. Y

Another important advantage of the present invention is that, due to thepivoted contact arm construction, a. greater pressure is applied to thecontacts and a wiping action between the contacts is effected as thecontacts start to open. As the switch arm 21 starts to move the contactarm pivot 25 away from the bese Ii, the spring 11 rocks the. contact arm25 clockwise about its pivot maintaining the'tip of the'contact `2| inengagement-with the stationary contact |1. At the same time theclockwise rotation of the contact arm 25 moves the line of action of thespring anV additional distance above the pivot 25, thus increasing thepressure` applied by the spring 11 to the contact and causes the tip of.the contact 2| to wipe along the face .of thel stationary con-V tact |1during the initial opening movement.

In ordinary circuit breakers when the contacts wear, the result is adecrease in the pressure applied to the contacts due to the lengtheningof the contact springs. Another important feature' cation of increasedcontact pressure as the contacts wear. Referring to Fig. 2, it isobvious that as the faces of the contacts l1 and 2| wear, the contactarm 25 is permitted to rock farther in a clockwise direction about itspivot 25 which moves the line of action of the spring 11 farther abovethe pivot 25 permitting the spring to apply increased pressure on thecontacts.

Following each automatic opening of the breaker due to an operation ofthe trip device, it is necessary to reset the mechanism to an operativecondition before the circuit breaker can be reclosed. To reset themechanism the lever 41 is rotated from the position in which it appearsin Fig. 3 to its extreme counterclockwise or open position. Movement ofthe lever 41 is transmitted to the cradle 55 by means of a hookprojection I 5| which engages a portion |52 ofthe cradle 55 and rocksthe cradle counterclockwise therewith.` As the cradle 55 is rotated, thelatching end thereof passes the latch member and engages a projection|55 on the trip bar 51 rocking said trip bar clockwise slightly pastnormal position. At

this rotation of the trip bar the projection ,l I5

thereon rocks the. latch lever 93 counterclockwise compressing thespring |55 and 4reengaging the lever 53 with the latch |55. 'I'he latchmember now has assumed its normal latching position in the path of thecradle 55.

' After the cradle 55 has been rentened, the con-y tacts may be closedmanually by movin'g the handle 53 clockwise to its closed circuitposition.

-During this movement of the handle, the line of sition, the arm 25strikes a projection |51 on the` base at a point to the left of thepivot25 (Fig. 2), causing clockwise rotation of the arm 25 about its pivot 25and moving the line of action of the spring 1'| overcenter above thepivot 25. The effect of this action is to cause a very quick snap actionto close the contacts and to provide a more stable contact pressurewhich prevents bouncing or chattering of the contacts upon closure.

In order to open the contacts manually, the operating lever 41 is movedcounterclock-wise about its pivot. This movement carries the line ofaction of the springs 53 to the left of the pivot axis 59 of the togglelink 45 and the-force exerted by the vsprings 53 now biases the toggle-5I away from its overcenter position.l Before the lever-.541 reachesits extreme counterclockwise orl j")pen position, this force becomessui'liciently great to cause the toggle to collapse.

Since thetoggle link 5| is pivotally connected to the switch, 'arms-21for the center pole, the arms 21 for vv,all 'of the poles are rotated ina counterclockwise direction, causing simultaneous opening of thecontacts for all of the poles of the breaker. The contacts are closedmanually in the previously described manner.

The circuit breaker is entirely trip free. that is. it operatesautomatically in response to an overload to open the contacts regardlessof the position of the operating lever 41.

The arc extinguishers i9, there being one provided for each pele of thebreaker, are of the .spaced plate type, and comprise, generally.. a

of the instant invention is the automatic appli'- 75.

stack of slotted'plates of magnetic material positioned adjacent thepaths of movement of theV contacts 2|. s The presence of these platescauses the arc resulting from the rupture of the circuit to be drawn inthe direction toward the ends of the slots which results in the breakingup of the arc into a plurality of short arcs and causes said arcs to becooled and extinguished.

Fig. 4 illustrates a modified form of the contact arm 25. In this gure,the parts are shown in closed circuit position by the full lines and inopen position by the dot and dash lines. The contact arm is providedwith a hook projection |59 which, in the closed contact position,projects into an opening |6| in a plate |63 secured to the base of thebreaker. When the breaker is opened either automatically or manually andthe arms 21 rock counterclockwise, the projection |59- engages the upperedge of the opening |6| causing the contact arm 25 to rockcounterclockwise about its pivot 26. When this occurs, a spring |65compressed between the bracket 8| and a shoulder on va rod |61 pivotallyconnected to the contact arm25 by a pivot pin |69, is moved below thecenter line 26`|69 and acts to complete the counterclockwise movement ofthe contact arm 25 about the pivot 26. The projection |59 moves free ofthe opening |6| permitting the arms 21 to carry the contact arm 25 tofully open position as indicated by dot and dash lines (Fig. 4).

When the switch arms 21 are rocked to close the contacts, as abovedescribed, the toggle formed by the rod |61 and the contact arm 25remains in the position indicated by dot and dash lines (Fig. 4) untilthe contact arm strikes the top of the plate |63 which thereupon causesclock-- wise rotation of the contact arm. 25 about its pivot 26. At thismovement, the projection |59 reenters the opening |6| and the line ofaction of the spring |65 moves above the center line 26-| 69 causing thecontacts to close with a snap action. In the closed position, thevspring |65 applies pressure to the contacts |1-2|.

The operation and advantages of this modiilcation of the contact armconstruction are the same as described in connection with the originalembodiment. The construction of this modification provides greatercontact separation, higher speed operation of the contacts, wipingaction of the contacts, increased contact pressure during the initialopening movement and also -when the contacts wear down, and preventsvibration or oscillation of the moving contacts, the same as in theoriginal embodiment.

The, remaining structure of the circuit breaker and its operation is thesame as shown and described. in connection with' the originalembodiment.

Certain features of the circuit breaker and trip device constructionillustrated and described in this application are disclosed and claimedin our copending application for Circuit breaker, Serial No. 399,457,led June 24, 1941, and assigned to the assignee of the presentinvention.

Having described several embodiments of the invention in accordance withthe patent statutes, it is to bel understood that various changes andmcdications may be made in the structural details disclosed withoutvdeparting -from some of the essential features of the invention. It is,therefore, desired that the invention. be intelpreted as broadly as theprior art permits, and that it be limited only by what is expresslystated in the following claims.

We claim as our invention:

1. In a. circuit breaker, the combination" of relativelymovableeontacts'including a stationary contact and a movable contact, aswitch arm movable to open and close the contacts, actuating means formoving said switcharm, a contact arm pivotally mounted on the switcharm, said movable contact being mounted on said contact arm, meanscooperating with said contact arm to form a toggle disposed for movementwith the switchv arm, and means engageable by said toggle when theswitch arm is moved to open the contacts to cause said toggle to movethe contact arm about its pivot in an opening direction.

2. A circuit breaker comprising a stationary contact, a movable contact,a switch arm movable to open and close the contacts, actuating means formoving the switch arm, a contact arm pivotally mounted on the switcharm, a toggle link cooperating with the contact arm to form a toggledisposed for movement with the switch arm, and a xed member engageablebythe toggle when the switch arm isi moved to open and to closedpositions to cause the toggle to move the contact arm about its pivot toopen and close the contacts with a snap action.

3. In a circuit breaker, the combination of relatively movable contactsincluding a stationary contact and a movable contact, a pvoted switcharm movable to open and close the contacts, a contact arm pivotallymounted on said switch arm, the movable contact being secured on saidcontact arm, actuating means for movingr the switch arm, a springactuated member cooperating with the contact arm to form a togglemounted for movement with the switch arm, means engageable by saidtoggle when the switch arm is moved tov open position toy cause saidtoggle to move the contact arm about its pivot in an opening direction,and engageable by the toggle when the switch arm is moved to .close thecontacts to cause said toggle to move the contact arm about its pivot ina. closingV direction with a snap action.

4. A circuit breaker comprising relatively movable contacts, a movableswitch amr, av contact arm pivotally mounted on said switch arm, saidcontact arm having one of said contacts mounted thereon, operatingmechanism for moving the switch arm to open and closed positions,y meanscooperating with thev contact arm to form` a toggle for moving the.contactarm; about its pivot, said vtoggle being movable the switch armyand means engageable by the: toggle for causing said toggle to move the.contact ann. about its pivot to open and', closed; positions whenv theswitch arm is moved to open and closed positions.

5. A circuit breaker comprising a stationary contact and aV movablecontact, a switcharm movable to cause openingv and closing of thecontacts, operating mechanism for moving the switch arm to open andclosed positions, a contact arm pivotally mounted. on the switch arm.and having said movable contact mounted thereon, means cooperating withsaid contact arm to form a toggle movable with the. switch arm forrotating the contact arm, means engageable by said toggle when theswitch. arm. is moved to open position for moving the contact arm aboutits pivot in a direction away from the stationary contact, and othermeans engageable by the toggle when the switch arm. approaches closedposition for moving the contact ann about its pvot in a directiontowards the stationary concontact, a pivotally mounted switch arm, acontact member pivotally supported on said switch arm and adapted tocooperate with the stationary contact, actuating means for rotating theswitch arm about its pivot to open and close the contacts, a togglemember cooperating with the contact member to form a toggle, and meansengageable by said toggle when the switch arm is rotated to open thecontacts to move said toggle overcenter in a direction to cause movementof the contact member about its pivot in an opening direction. i

'1. In a circuit breaker, the combination oi' a stationary contact and amovable contact, a switch arm movable to open position and to closedposition, actuating means for moving the switch arm to open and closethe contacts, said contacts forming the sole means for interrupting thecircuit, a contact arm pivotally mounted on the switch arm, a springactuated toggle link cooperatingwith the contact arm to form a toggle,said toggle being disposed for movement with the switch arm, and meanscomprising an insulating member engageable by the toggle when the switcharm is moved to closed position to cause the tog- 81e to move overcenterin 'a direction to close the contacts with a snap action, said toggleacting to apply pressure to the contacts when they arev closed.

8. In a circuit breaker, the combination of a stationary contact and amovable conta-ct. a switch arm movable to open and closed positions, acontact arm pivotally supported on theswitch arm, actuating means formoving the switch armto open and close the contacts,` a spring actuatedmember cooperating with the contact arm to form a toggle movablewith-the switch arm, and means iirst part of the opening movement of theswitch arm for moving the toggle overcenter in a direc tion to causemovement of the contact arm about its pivot in an opening direction witha snap action, said means beingengageable by the toggle when the switcharm approaches closed position for moving the toggleovercenter in adirection to cause the contacts to close with a snap action.

9. In a 'circuit breaker, the combination of relativelymovable contacts,a switch armmovable to open and closed positions, a contact armpivotally mounted on the switch arm, actuating means including a togglefor moving the switch arm to open and close the contacts, an overcenterengageable by the toggle during the spring operatively associated withthe contact arm for actuating said contact arm about its pivot and afixed member engageable by said contact arm upon movement of the switcharm to open and closed positions to initiate movement of the contact armabout its pivot in opening and closing directions respectively.

10. In a circuit breaker, `the combination of relatively movablecontacts, a pivoted switch member movable to open and closed positions,a contact arm pivotally supported on the switch member, actuating meansfor moving the switch member to open and close the contacts, and meanscooperating with the contact arm to form a toggle, said toggle beingengageable with a ilxed member upon movement oi! the switch member toopen and closed positions t0 actuate the contact arm about its pivot inopening and closing directions.- l

11. In a lcircuit breaker, the combination of relatively movablecontacts, aswitch member movable to open and close the contacts, acontact arm pivotally supported on the switch member, actuating meansfor the switch member, and a spring biased toggle link movable with theswitch member and cooperating with the contact arm to form a toggle,said toggle during the first part of the opening movement of the switchmember being eifective to apply increased pressure to said contacts, andixed means engageable by said toggle at a predetermined point in theopening movement oi' the switch member to initiate actuation oi.' saidcontact arm about its pivot in opening direction.

l2. A circuit breaker comprising a stationary contact, a pivoted switchmember movable to open and to closed circuit position, a contact armpivotally mounted on the free end of said switch member for cooperatingwith said stationary contact, means comprising a compression springassociated with. said contact arm and said switch member for actuatingsaid contact arm about its pivot, a guide link for supporting saidspring pivotally engaged at one end 4with one end of said contact arm, aguide mounted on said switch member adjacent the pivoted endv thereoffor slidably supporting the other end of'said guide link, said springbeing disposed between said guide and a shoulder on said link.

Hmm?, D. DORFMAN. GERALD J. FREESE.

